Rotary drilling operations for oil and gas wells generally employs a drill string consisting of many joints of drill pipe at the top of the string and several joints of drill collars at the bottom of the string nears the bit.
Periodically during the drilling of a well the drill string, partially or entirely, must be removed from the hole. Such cases include the need for changing bits, running casing or for other reasons. Also, as the drilling progresses and the borehole becomes deeper, additional joints or stands of pipe must be added for drilling to continue.
To add or remove drill pipe or drill collar segments to or from the drill string, the existing connections between the drill pipe or drill collar segments must be broken loose and then rotated multiple times to disengage the threaded connection and separate the segments so the segments may be removed from the drill string. The pipe sections, known as “stands” of pipe may be comprised of one or more individual pipe joints depending on the particular configuration of the drilling rig. When the pipe string is reassembled into the well bore, the opposite procedure is followed. The pipe sections must be reinserted, rotated clockwise and retightened before drilling can recommence. For these operations, current art often utilizes large machines known as “iron roughneck” machines, to hydraulically make these connections. When recombining the pipe segments into a continuous string inside the well bore, it is necessary to guide the next stand to be added into alignment with the drill string suspended in the well bore. This portion of the operation is known as “stabbing the pipe”. On large or specialized rigs, expensive and complex pipe handling machines are sometimes used to move pipe between the setback area or pipe rack and the well center in preparation for reattaching the next pipe segment in the string. On most rigs, however, the pipe is lifted with elevators attached to the rig's hoisting equipment and the male threaded segment of the tool joint, or “pin”, is manually guided into alignment with the female threaded segment of the tool joint, or “box”, of the drill string suspended in the well bore. Due to the movement of the pipe being added, this process is somewhat inexact and “mis-stabs” are common, resulting in scarring of the sealing face of the tool joint. Due to the proximity of the rig personnel to the well center, it is also somewhat dangerous.
When using an “Iron Roughneck” type machine, much of the danger for the rig personnel is reduced during tripping operations but the risks inherent in manually stabbing pipe remain.
Additionally, when tripping with manual tongs, in order to speed operations, it is common to clamp the lower tong onto the box portion of the tool joint of the top segment of the drill string the suspended in the well bore before stabbing the pin portion of the next stand of pipe to be added into it. When using an iron roughneck, this practice is seldom used because of the increased risk of injury from accidental pinching of the hands of the rig personnel between the moving pipe and the stationary iron roughneck. Current practice when using an iron roughneck is to wait until the pipe is manually stabbed before engaging the iron roughneck with the drill string. This delay results in lost rig time.